This A1C to average blood sugar calculator and conversion chart helps you translate an A1C percentage into an estimated average glucose (eAG) value in mg/dL or mmol/L. Use it to understand the relationship between a laboratory A1C result and your home blood sugar readings, while remembering that an estimate is not a diagnosis or a replacement for advice from your healthcare team.
Overview
A1C, also called hemoglobin A1C or HbA1C, reflects the amount of glucose attached to hemoglobin in red blood cells. Because red blood cells circulate for several months, A1C provides a longer-term view of blood sugar than a single finger-stick or continuous glucose monitor reading.
Estimated average glucose, or eAG, expresses an A1C result in the same units commonly used by glucose meters. This can make an A1C report easier to compare with daily readings. However, eAG is an average—not a prediction of what your blood sugar should be at every moment. Two people with the same A1C may have very different patterns, including different fasting, after-meal, overnight, and low blood sugar readings.
The chart below uses the commonly used conversion relationship:
- eAG in mg/dL: (28.7 × A1C) − 46.7
- eAG in mmol/L: eAG in mg/dL ÷ 18
These calculations are approximate and are intended for education. Your laboratory report, glucose meter, or care team may provide slightly different information because of measurement variation and individual biology.
| A1C | Estimated average glucose (mg/dL) | Estimated average glucose (mmol/L) |
|---|---|---|
| 5.0% | 97 | 5.4 |
| 5.5% | 111 | 6.2 |
| 6.0% | 126 | 7.0 |
| 6.5% | 140 | 7.8 |
| 7.0% | 154 | 8.6 |
| 7.5% | 169 | 9.4 |
| 8.0% | 183 | 10.2 |
| 8.5% | 197 | 10.9 |
| 9.0% | 212 | 11.8 |
| 10.0% | 240 | 13.3 |
| 11.0% | 269 | 14.9 |
| 12.0% | 298 | 16.6 |
For context, an A1C result is only one part of diabetes management. Treatment goals vary according to factors such as age, pregnancy, diabetes type, other health conditions, medications, risk of low blood sugar, and personal preferences. Do not change insulin, other diabetes medication, or eating patterns solely because of this chart.
How to estimate
To use the A1C calculator, start with the exact A1C percentage on your laboratory or clinic report. Enter the number as a percentage, not as a decimal. For example, an A1C of 7.2% should be entered as 7.2.
Next, apply the formula:
(28.7 × 7.2) − 46.7 = approximately 160 mg/dL
To convert that result to mmol/L, divide by 18:
160 ÷ 18 = approximately 8.9 mmol/L
Round the result to a practical whole number in mg/dL or one decimal place in mmol/L. Avoid treating a small difference—such as 159 versus 160 mg/dL—as meaningful. The goal is to understand the general range and compare it with your broader glucose record.
A useful next step is to review several days of readings rather than one isolated value. A blood sugar log with meal and A1C notes can help you record fasting readings, pre-meal values, post-meal checks, activity, medication timing, and symptoms. This context may reveal patterns that an A1C cannot show.
Inputs and assumptions
The calculator requires one main input: an A1C percentage. The conversion assumes that the A1C reasonably represents your recent average glucose. That assumption is not equally reliable for everyone.
Your A1C may not match your meter or CGM average for several reasons. Glucose can change quickly, while A1C changes more gradually. A person with frequent highs and lows may have the same average as someone whose readings stay close to the average. Differences in testing devices, timing, missed readings, sensor gaps, and recent changes in treatment can also affect comparisons.
Conditions that affect red blood cells or hemoglobin can make A1C less dependable. Examples may include certain anemias, recent blood loss or transfusion, kidney or liver problems, hemoglobin variants, and pregnancy-related changes. Some medications or medical treatments may also influence the result. If your A1C and home readings consistently disagree, tell your healthcare professional rather than trying to correct the numbers yourself.
The chart also does not tell you whether a reading is safe at a particular moment. Symptoms of low blood sugar, very high readings, dehydration, vomiting, confusion, or difficulty breathing require prompt attention according to your individualized sick-day and emergency plan. People who use insulin or have type 1 diabetes should follow their care team's instructions about ketone testing and urgent care.
Worked examples
Example 1: A1C of 6.4%
(28.7 × 6.4) − 46.7 = approximately 137 mg/dL, or about 7.6 mmol/L. This is an estimated average, not a recommended daily target. A person could still experience readings below or above this level during the day.
Example 2: A1C of 8.1%
(28.7 × 8.1) − 46.7 = approximately 186 mg/dL, or about 10.3 mmol/L. Reviewing meal timing, medication use, activity, illness, sleep, and glucose patterns with a care team may help identify practical next steps.
Example 3: A1C of 9.5%
(28.7 × 9.5) − 46.7 = approximately 226 mg/dL, or about 12.6 mmol/L. This result deserves a planned clinical discussion, particularly if it is new, rising, or accompanied by symptoms. A carb-counting meal plan template may help organize questions and observations, but it should support—not replace—individual medical advice.
These examples illustrate why an A1C-to-average-blood-sugar conversion is useful for orientation but limited for decision-making. Your clinician may focus on time in range, fasting readings, post-meal patterns, hypoglycemia, or other measures in addition to A1C.
When to recalculate
Recalculate whenever you receive a new A1C result and want to compare it with your glucose log. It can be especially helpful after a meaningful change in medication, insulin routine, meal pattern, physical activity, illness recovery, weight, or monitoring method. Keep the date beside each result so you can see the direction over time rather than focusing on one number.
- Record the A1C percentage and test date.
- Convert it using the formula or chart above.
- Compare the estimate with several weeks of available meter or CGM data.
- Note whether the readings include lows, overnight changes, or after-meal spikes.
- Write down questions for your healthcare team before changing treatment.
Revisit this page when a new A1C is available, when your monitoring data changes, or when your clinician asks you to evaluate a new goal. If your results are unexpectedly different from your usual pattern, arrange a medical review. For broader diabetes management, related resources on diabetes and kidney health and diabetes and blood pressure can help you prepare for a more complete discussion of your health.
